128 MANUAL OF NATURAL HISTORY. 



simple at base; tentacles close together at 

 base ; mantle-lobes expanded, covering sides 

 of shell; operculum none ; shell polished, with 

 plaits on pillar ; margin of outer lip thick- 

 ened. (Marginellidce, Auct.) 



10. Family. — Fissure-Shells (Turritidse). Siphon 



straight ; mantle with a slit on hind part of 

 right side ; shell turreted ; aperture with a 

 straight canal in front ; outer lip with a fis- 

 sure or sinus at hind part of margin. (Pleu- 

 rotomidce, Gray.) 



11. Family. — Tun-Shells (Doliidse). Mantle en- 



closed ; siphon recurved ; foot small ; oper- 

 culum none ; shell thin, ventricose, witl 

 transverse ribs or grooves ; aperture with an 

 oblique notch in front. 



12. Family. — Fig-Shells (Sycotypidse). Mantle 



with expanded lobes covering sides of shell ; 

 siphon produced ; operculum none ; shell 

 light, ventricose ; aperture with a produced 

 canal ; whorls with transverse ribs. (Ficula, 

 Swains.) 



13. Family. — Velvet-Ears (Velutinidae). Eyes on 



outer side of tentacles ; margin of mantle in- 

 flated, folded on the edge into two canals; 

 operculum none ; shell thin, turbinate, co- 

 vered with a velvety epidermis ; aperture 

 wide, simple in front. 



14. Family. — Dwarf -Ears (Otinidse). Tentacles 



obsolete ; eyes on upper part of head ; man- 

 tle enclosed; foot divided by a transverse 



